Implement QoS on request level

[mgroen2]

Currently you can only set QoS (value for page load time, TTFB) values for tests.

However I need to be able to set QoS on specific pages (or even better) specific requests/responses.

So in my opinion LC could be improved by implementing QoS values on requests/responses. See attached screenshot.

[AlexKaras]

Considering, that one always can make a specific Connection to be the only part of Page, I think that it would be enough to be able to override QoS on the Page level.

QoS parameter on the Page level should have two values: Default and Custom, where Default means that the exact value corresponds to the one defined in the Test that executes this scenario and Custom makes it possible to specify the value that will be used during the test (and test that contains this scenario).

From the usability point of view, I think that the pages with overridden QoS value should be visually outlined in the Scenario Editor.